Conventionally the injection-molded-in foil decoration by which a plastic molding is formed, and simultaneously therewith patterns, etc. are applied by decoration sheet to the surface of the plastic molding being formed is performed in various modes.
For example, the bulletin of Japanese Patent Publication No. 19132/1975 discloses a process for integrating a decoration sheet with the surface of an injected molding at the same time of the injection molding, in which a female mold for vacuum forming having a vent hole is used as a vacuum forming mold, a decoration sheet is fed and set on the female mold, then is thermally softened by a hot platen to be preformed by vacuum forming and contoured to fit the cavity surface of the female mold, then the male and the female molds are clamped, next molten resin is injected in a cavity defined by both molds, and the molds are opened to take out a molding.
For example, the bulletin of Japanese Patent Laid-Open Publication No. 315950/1994 discloses a technique of decorating the surface of a molding by a decoration sheet at the same time of forming the molding, in which a web decoration sheet payed out from a roll is fed between a pair of male and female molds in their opened state and is fit at the boundary portion to the parting face of the female mold by a sheet presser frame to be thereby fed onto the female mold, then a hot platen is moved into between both molds from a withdrawn position outside the mold to be opposed to the decoration sheet fed on the mold so as to incontiguously thermally soften the same so as to preform the decoration sheet in the injection mold to contour the decoration sheet to fit the cavity surface of the female mold, then the hot platen is withdrawn to the withdrawn position outside the mold, both molds are clamped, resin is injected into the cavity defined by both molds, the molds are opened, and the molding is taken out.
In these modes, the decoration sheet is preformed by an injection mold, and the decoration sheet is thermally softened for the preforming after the decoration sheet been fed on the mold.
The bulletin of Japanese Patent Publication No. 42172/1992 discloses the technique for feeding a decoration sheet on a mold and thermally softening the same in the mode that the decoration sheet is preformed by an injection mold, in which a hot platen is reciprocated, for thermally softening the decoration sheet, between the inside of the mold and a withdrawn position thereof outside the mold, and has air holes formed in the heating surface thereof, the decoration sheet is sucked on the heating surface and further pressed fit to the heating surface by a frame member, whereby the hot platen is in the withdrawn position retains the decoration sheet on the heating surface and is moved into the mold, retaining the decoration sheet on the heating surface.
However, the modes described in the bulletins of Japanese Laid-Open Publication Nos. 19132/1975, and 315950/1994 described above and others, wherein the decoration sheet of a distortion temperature or less than the distortion temperature is fed on the mold at room temperature and then heated has a disadvantage that when a decoration sheet of good heat resistance or a thick decoration sheet is used, it takes time to heat the decoration sheet, thus causing a long cycle time, which lowers productivity.
In the bulletin of Japanese Patent Publication No. 42172/1992 described above a decoration sheet can start to be heated when the heater plate is at its withdrawn position. A heating time after the heater plate has been moved into a mold can be accordingly shorter. However, because the decoration sheet is drawn on the heating surface and retained thereon, impressions of vent holes formed in the heating surface are made on the softened decoration sheet, which makes the appearance poor. In cases of especially large decoration sheets or thick decoration sheets, sometimes vacuum for drawing and retaining the decoration sheets causes leaks, and the decoration sheets are torn off. It is difficult to completely suppress deformation and distortion of the decoration sheets when the softened decoration sheets are conveyed inbetween the male and female molds. Furthermore, when the decoration sheets are fed to the female mold which is to be a preforming mold, the heater plate releases the decoration sheets drawn thereon by suction through the vent holes and oppositely blows out compressed air through the vent holes, and in addition thereto, the decoration sheets are already heated. Accordingly, when the decoration sheets are left from the heating surface one after another at a small time interval, sometimes the decoration sheets wrinkle, or transfer of the decoration sheets is unstable. In the case where a decoration sheet has an adhesive layer on the back side, sometimes the adhesive layer remains on the heater plate.